The present invention concerns a semiconductor device and a method of manufacturing the semiconductor device.
For example, International Laid-Open Publication WO2009-001706 discloses a magnetoresistive random access memory (MRAM) utilizing a current driven magnetic domain wall motion.
FIG. 12 shows a configuration of an MRAM disclosed in International Laid-Open Publication WO2009-001706. The MRAM has first magnetization pinning layers 5a, 5b, a second magnetization pinning layer 6, a non-magnetic layer 4, and a free magnetization layer. The free magnetization layer has a magnetization pinned regions 1a, 1b, a magnetic domain wall moving region 3, and magnetic domain wall pinning sites 2a, 2b. The second magnetization pinning layer 6 is disposed so as to overlap at least a portion of the magnetic domain wall moving region. Each of the free magnetization layer, the first magnetization pinned layers 5a, 5b, and the second magnetization pinning layer 6 comprises a ferromagnetic material and shows magnetization indicated by the direction of arrows. That is, the first magnetization pinning layers 5a, 5b have pinning magnetization anti-parallel to each other, and the second magnetization pinning layer 6 has pinning magnetization in parallel to the first magnetization pinning layer 5a or 5b. 
The magnetic domain wall moving region 3 of the free magnetization layer can be optionally switched for magnetization in accordance with writing of current and serves for writing information. The magnetization pinned regions 1a, 1b of the free magnetization layer are disposed in adjacent with the first magnetization pinning layers 5a, 5b by which the magnetization pinned regions 1a and 1b have magnetization anti-parallel to each other.
Further, a magnetic domain wall is formed to the magnetic domain wall pinning site 2a or 2b in accordance with the direction of magnetization of the magnetic domain wall moving region. The magnetic wall pinning site has a function of stably fixing the magnetic domain wall when a magnetic field or current is not applied. It has been theoretically found that the magnetic domain wall pinning sites 2a, 2b in the free magnetization layer can spontaneously fix the magnetic domain wall with no provision of particular structure.
Japanese Unexamined Patent Application Publication No. 2003-174149 discloses the structure of magnetoresistive random access memory (MRAM) suitable to refinement and integration.
The MRAM comprises a cylindrical first magnetic body capable of changing the magnetization direction and opened at one end and a columnar second magnetic body fixed in one peripheral direction for the direction of magnetization and formed in the cylinder of the first magnetic body by way of an insulating layer. A rotating magnetic field is generated by flowing a tunnel current between the first and second magnetic bodies to set the direction of magnetization of the first magnetic body to one or another peripheral direction, and utilize the change of the magnetic resistance depending on the direction of magnetization of the first magnetic body to the direction of magnetization of the second magnetic body as binary signals.
Japanese Unexamined Patent Application Publication No. 2009-224477 discloses a magnetic memory unit having an MRAM and a manufacturing method thereof.
Specifically, it relates to a structure of an MRAM containing a magnetization pinning layer, a non-magnetic spacer layer formed over the magnetization pinning layer, and a free magnetization layer formed over the non-magnetic spacer layer in which the magnetization pinning layer and the free magnetization layer are adjacent to each other with a non-magnetic spacer layer being interposed therebetween in a device region of the magnetization pinning layer except for the peripheral portion, and the magnetization pinning layer and the free magnetization layer are spaced apart on the peripheral portion of the magnetization fixing layer.